The invention is directed to a process for information transmission and, more particularly, to a process for transmitting information entities serially between subscribers connected by a serial bus.
Increasingly, data processing technique makes use of networks of computers or the like. Different bus systems are known for these network functions. The information stream between a number of electronic components (for example, between control devices) also continues to increase in automobile technology. For example, the so-called CAN system (CAN=Controller Area Network) (cf. DE-OS 35 06 118) or ABUS system (ABUS=Automobile Bit-Serial Universal Interface) are presently used in motor vehicles for linking individual components. The objective of every communications system is to link individual components (subscribers) via bus lines so that they can communicate with one another via a central system or e.g. via an externally connected tester. In this respect there is a special case of communications relating to diagnostics. In this case an external testing device addresses one or more control devices for interrogating corresponding states. Due to competing subscribers, the problem of so-called bus arbitration occurs regardless of the type of bus system. Thus, it must be ensured that no more than one subscriber occupies the bus at one time, since this would lead to inaccurate information and/or loss of information. Like the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) which is used to manage an ETHERNET bus, the aforementioned systems (CAN, ABUS) also work on the principle of priority ranking and checking of the transmitted information. In the case of CSMA/CD mentioned above, the information is lost in the event of collision and must be retransmitted. In CAN and ABUS, the message with higher priority is transmitted and the message with lower priority must be retransmitted. The known processes require independent hardware for bus connection and management.